The insulinotropic peptide hormone glucagon-like peptide (GLP-1) has been implicated as a possible therapeutic agent for the management of type 2 non-insulin-dependent diabetes mellitus as well as related metabolic disorders, such as obesity. Other useful insulinotropic peptides include exendin 3 and exendin 4. While useful, GLP-1, exendin 3 and exendin 4 suffer from limited duration of action associated with short plasma half-lifes in vivo, mainly due to rapid serum clearance and proteolytic degradation. The enzyme responsible for the degradation of GLP-1, dipeptidyl peptidase IV, has been identified. Extensive work has been done in attempts to inhibit the peptidase or to modify GLP-1 in such a way that its degradation is slowed down while still maintaining biological activity. Despite these extensive efforts, a long lasting, active GLP-1 has not been produced. As such, the diabetic community has a tremendous need for improved GLP-1, exendin 3 and exendin 4 peptides.
There is thus a need to modify GLP-1, exendin 3, exendin 4 and other insulinotropic peptides to provide longer duration of action in vivo, while maintaining their low toxicity and therapeutic advantages.